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University of Illinois Extension

Fall Armyworm

Frequency

2 (1 = rare 5 = annual) 

Severity

3 (1 = very little damage 5 = plants killed) 

Hosts

Sweet corn.    

Symptoms

Fall armyworm larvae are light brown to dark gray caterpillars with yellow and dark stripes. The caterpillar has an inverted Y on the head, four dots on the posterior end, and grows to 1-1/2 inches long. The adult moths are grayish, with grayish, white hind wings and a 1-1/2 inch wingspan.

Fall armyworm caterpillars feed in the whorl of late sweet corn crops but do not burrow into the stalk as does European corn borer. They also feed on the kernels of the ear, commonly attacking the side of the ear through the shucks. The external entry point into the shucks easily can be missed, but the damage to the kernels and associated frass (fecal material) are obvious once the ear is shucked.  

Life Cycle

Fall armyworms do not overwinter in Illinois but rather fly north each year. They most often arrive in southern Illinois in July and northern Illinois in August, though immigration can occur by June throughout the state.  

Management

Control fall armyworm during the late whorl stage and into the tasseling stage. Insecticide applications after silking has begun are not completely effective in preventing ear damage.


Filed under plants: Vegetables

Filed under problems: Insects Damage

More information is available on Hort Answers.